Eureka

Eureka is a REST (Representational State Transfer) based service that is primarily used in the AWS cloud for locating services for the purpose of load balancing and failover of middle-tier servers.

At Netflix, Eureka is used for the following purposes apart from playing a critical part in mid-tier load balancing.

For aiding Netflix Asgard - an open source service which makes cloud deployments easier, in
* Fast rollback of versions in case of problems avoiding the re-launch of 100's of instances which
could take a long time.
* In rolling pushes, for avoiding propagation of a new version to all instances in case of problems.

For our cassandra deployments to take instances out of traffic for maintenance.

For our memcached caching services to identify the list of nodes in the ring.

For carrying other additional application specific metadata about services for various other reasons.